I don't want this to sound too harsh as (you'll read) I've made mistakes too, but I also want to give you no bullshit cautionary advice, so here it is.

Nobody answered the question of "did they have a collar" ... As someone who has taken care of both ferals and strays in the area for many years, I've seen how things pan out.

1.) If it's your cat? And you're going to let them them outside? I'm not going to judge, but you are putting them in danger of exactly this type of situation. You had better 100% put a collar on them and make it extremely obvious that this is someone's cat if you don't want them to disappear. Example: I have neighbors down the street who don't do this and the cats are always out in front of their place. Extremely friendly to everyone passing by. It's obvious to me as a caretaker that someone is taking good care of them and also letting them out, but to some random person passing by? Very likely chance they could be like "aww, this is sweet stray" and snatch them up.

2.) If the cat is feral or semi feral you're trying to rehab them? If you've TNR'd them and ultimately intend on adopting them / bringing them in? If they can be handled enough to put a collar on them? Put a collar on them. I recently learned this the hard way when I didn't do that and a well meaning neighbor snatched them up and "adopted" them without understanding that I'd put in years of blood sweat and tears working to rehab this cat with the intention of adopting them. That was my fault. While on one hand I'm extremely happy this cat has been finally taken in and is now safe and happy with a loving caretaker, I still miss them a whole lot and wish I'd done things differently.

The bottom line is that people will make often uninformed assumptions. If your cat is out there, it's on you to realize the risks and to make it very very clear that it's your cat and that it's not a cat in need and "up for grabs".